Synonyms
Airflow–pressure drop relationship; Resistance to airflow
Definition
The resistance, which has to be overcome by air flying through porous media such as plant tissues and a packed bed of plants and agricultural products (e.g., bulk grain), is defined as a pressure drop per unit depth.
When air is forced through a layer of porous materials, resistance to the flow, the so-called pressure drop, develops as a result of energy lost through friction and turbulence. The prediction to airflow resistance is necessary, for example, to the fan selection for grain drying and aeration systems.
Ergun’s model is the most comprehensive model to be used for airflow–pressure drop calculations. Ergun assumed that the pressure loss can be treated as the sum of the viscous and kinetic energy losses. The model is the sum of equation for laminar flow (this term is a linear function of airflow rate) and equation for turbulent flow (this term is a function of v 20 ) and has the following form:
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Bibliography
Pabis, S., Jayas, D. S., and Cenkowski, S., 1998. Grain Drying: Theory and Practice. New York: Wiley.
Smith, E. A., 1995. Forced air distribution for in-bin drying and aeration. In Jayas, D. S., White, N. D. G., and Muir, W. E. (eds.), Stored-Grain Ecosystems. New York: Marcel Dekker, pp. 569–607.
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Kaleta, A., Górnicki, K. (2011). Air Flux (Resistance) in Plants and Agricultural Products. In: Gliński, J., Horabik, J., Lipiec, J. (eds) Encyclopedia of Agrophysics. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-3585-1_12
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DOI: https://doi.org/10.1007/978-90-481-3585-1_12
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